This study from MIT used geo data collected from cars in Milan, Italy, to check the effectiveness of 30 km/h zones in reducing speed.

The first conclusion is that the signs don’t work: 85 percentile speeds are all over the place in 30 km/h zones in Milan, as shown in the figure below:

85th percentile speed profiles of the 30 km/h zones in the City of Milan.

The second step was finding correlations between speeds and street features extracted from openstreetmap. Results are as expected: narrow, short, curvy sections correlate with lower speeds, as do 1 lane vs more, one way vs 2 ways:

OSM features comparison between high and low compliance Zones 30. We report the features with the lowest 𝑝-values in the Mann-Whitney U test. All 𝑝-values are below 0.001.

The final step is also interesting: the authors made a model to predict the compliance of 30 km/h speed limit on streets that are 50 km/h at the moment. Useful for urban planning to understand if charging an area to 30 km/h would need structural interventions (like bumps, narrowing of the street…) or not:

Predicted speed 85th speed percentile with city-wide adoption of limit at 30 km/h

There is so much more in the article, I suggest to read it fully.

crossposted from: https://mastodon.uno/users/rivoluzioneurbanamobilita/statuses/114827312307353297

  • roscoe@lemmy.dbzer0.comEnglish
    2·
    1 year ago

    People drive at whatever feels safe. If I’m driving down a 5-7 lane stroad with wide lanes, I’m doing 60mph+, I don’t give a shit what the limit is. Narrow the lanes, put in bike lanes with barriers, street parking (if any) outside the bike lanes next to the driving lanes, add crosswalks with flashing yellow lights, I’ll cut my speed in half or more because that’s what feels safe.

    Behavioral engineering is more effective than seemingly arbitrary signs.